Abstarct: In recent decades, science has been developing rapidly and mining is no exception too. Nowadays, new methods are introduced and designed for mining that are not part of the traditional surface and underground methods. One of these is the underground coal gasification (UCG) method. Coal due to its special chemical composition, can be change to oil or gas, and it is one of the most important sources of energy in the world. To start operations in each project, it requires to have a series of previous design and planning to take control of the operation. In the UCG method because of the lack of direct personnel access to the underground, this matter is more important. Also, due to the influence of various parameters on the successful implementation of this process and its complexity, the scientific gaps in this method is not completely solved as yet, and there is no complete information available for carrying out this operation on a commercial scale. One of the most important scientific gaps in this method is the lack of knowledge necessary to predict the shape and volume of the created cavity in underground and the amount and heating value of produced gas on a commercial scale. In this research, these two important issues have been discussed separately. At the first section, given the assumptive shape of the cavity in the single channel methods and the existing information in other's experiments, a series of equations have been introduced to predict the growth of cavity dimensions over time. Then a numerical modeling is developed by the COMSOL software to predict the volume of cavity. This model shows that volume of cavity is precisely predictable before start of UCG process. In the next section, by simulating the chemical reactions using the COMSOL software, it is possible to predict the amount and heating value of produced gas on commercial scale. Result of this model show that for producting syngas with more heating value; operating time, cavity pressure, steam injection rate and oxygen injection rate have the most positive effect, respectively. Finally, a case study was conducted for the K10 coal seam of takht area (in Iran). The Results show that to supply feed a power plant with power of 27 megawatt, for 22 years, 9 stopes must be active simultaneously. During of this period, amount of produced syngas from each stope is 5109 m3/s and from 9 stopes is 45987 m3/s, and heating value of syngas is 5964.1575 kcal/kg. Keywords: Underground Coal Gasification (UCG); Numerical simulation; Cavity growth rate; Amount of produced gas; Heating value of syngas; K10 coal seam of takht a